A Levitating Sphere Viscometer Operating in a Rotational Mode

We present a special operation mode of a levitating sphere viscometer which allows steady rotations of a levitated magnet around its vertical axis. In contrast to miniaturized oscillatory viscosity sensors, this mode of operation allows to obtain viscosity measurements more comparable to standard laboratory viscometers. Moreover, the measurement range is increased to higher viscosities, where no resonance peak is detectable in with oscillatory sensors. Using electromagnetical actuation and the readout, all fluids except ferrofluids are measurable. Due to the levitation and the contactless readout, only the measurement body has to be in contact with the fluid, all readout and actuation parts can be placed outside the measurement cell, which makes the setup particularly useful for, e.g., sterile, toxic or poisonous fluids.